1. Field of the Invention
The present invention relates to a memorizing medium cartridge such as a disk-shaped information memorizing medium cartridge in which an information memorizing medium such as an optical disk, a magneto-optical disk and the like is accommodated in a state of rotating freely and particularly to a memorizing medium cartridge capable of effectively restraining minute dust from entering in a cartridge housing while it is in a state of being reserved.
2. Description of the Related Art
In the past, generally, as an information memorizing cartridge in whose housing an information memorizing medium capable of recording and/or reproducing information such as audio, video, computer data and the like is accommodated in a state of rotating freely , for example, a cartridge having an arrangement as shown in FIG. 1 has been known. This information memorizing cartridge is a disk cartridge 1 containing therein a write-once type magnetic disk where a user can record and write in information such as computer data and the like later on and has an outward appearance shape as shown in FIG. 1.
That is, this disk cartridge 1 comprises a cartridge housing 2 which is made up of a pair of upper and lower shells 2a and 2b, and an magneto-optical disk 4 accommodated in a state of rotating freely in a disk accommodating room 3 of this cartridge housing 2 and the like. On both surfaces of the upper and lower of the cartridge housing 2 are provided upper and lower opening windows 5 extending to one side from a central portion and this opening window 5 is made capable of being opened and closed by an opening and closing door 6 which is made capable of sliding along its one side. Then, at a central portion of the magneto-optical disk 4 is provided a hub portion 7 having a center hole 7a which is chucked to a turntable provided on a main body side of an information memorizing apparatus and this hub 7 is made to oppose a central portion of the opening window 5.
However, as the conventional disk cartridge having such an arrangement is structured such that the opening and closing door 6 is formed like a U letter shape to be fit in one side of the cartridge housing 2 and the opening window 5 is opened and closed by sliding the opening and closing door 6 along its one side, there has been a problem that a big gap forms between the cartridge housing 2 and the opening and closing door 6, thereby making it impossible to prevent the minute dust from intruding.
In this case, when the dust, which has intruded in the cartridge housing 2, attaches itself to a surface of an information memorizing surface of the magneto-optical disk 4, the read-out or write-in beam is shielded and the information memorizing surface is damaged by the dust, thereby making it impossible to carry out a read/write of information normally. Particularly, in a case of an information memorizing device with a large capacity, the effect of even minute dust can not be negligible and hence, there is a demand for a disk cartridge capable of preventing the intrusion of even the minute dust.
Further, in the above-mentioned conventional disk cartridge 1, because the opening and closing door 6 is located at a portion where it is easily touched by a user's hand, there is a fear that the user opens the opening window 5 by erroneously sliding the opening and closing door 6. Further, because the opening and closing door 6 moves linearly along one side of the cartridge housing 2, there is a problem that a surface area of the cartridge housing 2 can not be made smaller.
Also, as another example of the conventional memorizing medium cartridge, for example, there is a disk cartridge as is stated in a public bulletin of Japanese laid-open patent publication No. 7-6493. This disk cartridge comprises an upper case whose remaining half is circular-shaped and a remaining half is square-shaped, a lower case having the same shape as that of the upper case, two notch portions provided in a position which opens by 90 degrees in the circular shaped portions of the upper and lower cases when viewed from a disk center, a memorizing window provided at a center of the two notch portions of the lower case, a swinging shutter which covers the notch portions and the memorizing window and is fit in the circular portions of the upper and lower cases and a driven roller provided in a position symmetrical to the notch portions relative to the disk center in the upper and lower cases.
Although this disk cartridge is arranged such that the swinging shutter moves curvedly in the circular portion of the upper and lower cases, because the swinging shutter is formed in the same U letter shape as the above-mentioned opening and closing door 6 and this swinging shutter is so structured to fit in the circular portions of the upper and lower cases, a large gap similarly forms between the upper and lower cases and the swinging shutter, thereby giving birth to the problem that minute dust can not be prevented from intruding.